Theftproof lockable coupling device

ABSTRACT

A lockable coupling device for a truck trailer has a pin which can be moved axially out of baseplate for engagement with a coupling plate of a tractor. A shaft is operatively arranged to advance and retract the pin. The shaft is joined to a barrel rotatable by a crank. The barrel can be locked against rotation by a lock in the barrel. The crank carries a key for locking and unlocking the barrel. A motor may be provided to drive the shaft for extending the pin. The pin may be arranged to obstruct a hole in a coupling plate attached to a truck trailer. The pin can be provided with a spring for automatic retraction when the shaft is retracted. The rotatable barrel may have switch contacts connected in circuit with the motor. The motor may be driven electrically or hydraulically.

United States Patent Nagy et al.

[ Mar. 7, 1972 [54] THEFTPROOF LOCKABLE COUPLING DEVICE [72] Inventors: Charles E. Nagy, 3221 Benda PL, Hollywood, Calif. 90028; John F. Nagy, 785 West End Ave., New York, NY. 10025 221 Filed: Jan. 23, 1910 211 Appl.No.: 5,268

[52] US. Cl. ..280/433, 280/415 A, 70/187, 70/237, 70/393 [5 1] Int. Cl. ..B62d 53/08 [58] Field of Search ..280/433; 70/187, 237, 393, 70/232 [56] References Cited UNITED STATES PATENTS 3,082,020 3/ 1963 Hulverson et al ..280/433 1,150,406 8/1915 Watterson ..70/187 X 3,136,149 6/1964 Klein ..70/187 2,755,655 7/1956 Maffey ..70/232 Primary Examiner-Leo Friaglia Attorney-Polachek, Saulsbury & l-lough [5 7] ABSTRACT A lockable coupling device for a truck trailer has a pin which can be moved axially out of baseplate for engagement with a coupling plate of a tractor. A shaft is operatively arranged to advance and retract the pin. The shaft is joined to a barrel rotatable by a crank. The barrel can be locked against rotation by a lock in the barrel. The crank carries a key for locking and unlocking the barrel. A motor may be provided to drive the shaft for extending the pin. The pin may be arranged to obstruct a hole in a coupling plate attached to a truck trailer. The pin can be provided with a spring for automatic retraction when the shaft is retracted. The rotatable barrel may have switch contacts connected in circuit with the motor. The motor may be driven electrically or hydraulically.

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TI'IEFTPROOF LOCKABLE COUPLING DEVICE This invention relates to the art of devices used for coupling tractors and truck trailers, and more particularly concerns a coupling device provided with means for locking the same to prevent unauthorized coupling of a tractor to a trailer.

Heretofore truck trailers used for transporting bulk freight have been provided with protruding coupling pins or exposed sockets which could easily be engaged by mating coupling devices on tractors. Many thefts of trailers have occurred when highjackers coupled their tractors to loaded trailers and hauled the trailers away. The present invention is directed at preventing the unauthorized coupling of a tractor to a trailer by providing a coupling device which is lockable in such a way that an unauthorized tractor cannot be coupled to it.

According to the invention the coupling device has an axially movable or rotatable pin. The pin is axially movable by a worm drive. The worm is connected to shaft which is tumable by a crank. A lock is engaged with the shaft which is tumable by a crank. A lock is engaged with the shaft to lock it against rotation. The crank which turns the shaft is provided with a key to open the lock. In the absence of the crank and key assembly, the shaft cannot be turned to move the pin. In one form of the invention, the pin is arranged to retract in lock position so that the slotted coupling disk or fifth wheel" of a tractor cannot be engaged on the pin. In another form of the invention the pin is arranged to advance and obstruct a hole in a coupling plate attached to the trailer. This will prevent engagement with a coupling pin mounted on the coupling disk of a tractor. The device may also be provided with an electric motor for turning the shaft which turns the worm drive of the pm.

In another form of an invention a lockable screw drive is employed to advance a shaft having a tapered head. This tapered head advances a spring-biased pin having a tapered head. The pin, when advanced, obstructs a hole in a coupling plate attached to a trailer to prevent engagement by an unauthorized tractor. Alternatively the pin can be arranged to retract to prevent coupling with an unauthorized tractor.

In another form of the invention the key-operated lock closes an electric circuit which energizes an electric motor arranged to rotate the coupling pin. In this arrangement, the lock is mechanically separate from the worm drive of the pin.

In a further form of the invention the key-operated lock closes an electric circuit which actuates electrically operable hydraulic control valves. These valves control an air cylinder having a reciprocatable piston shaft mechanically connected via a linkage to the coupling pin for rotating it.

The invention will be explained in further detail with particular reference to the drawings, wherein:

FIG.. 1 is a vertical sectional view taken through a first coupling device embodying the invention, shown mounted in trailer body, with an associated crank-key shown in side view.

FIG. 2 is a perspective view of the crank-key on an enlarged scale.

FIG. 3 is an enlarged end view of the device taken on line 3-3 of FIG. 1.

FIG. 4 is a further enlarged vertical sectional view taken on line 4-4 of FIG. 3, but including parts of the crank-key, shown engaged with the device, the device being shown in locked condition.

FIG. Sis a reduced vertical sectional view taken on line 5 5 of FIG. 4.

FIG. 6 is a view similar to FIG. 4, showing the device in unlocked condition.

FIG. 7 is a diagram of the electric circuit including a motor drive of the coupling device.

FIG. 8 is a vertical sectional view similar to FIG. 1, showing a second coupling device embodying another form of the invention.

FIG. 9 is a reduced bottom plan view, taken on line 9-9 of FIG. 8.

FIG. 10 and FIG. 11 are vertical sectional views of third and fourth coupling devices respectively, embodying other forms of the invention.

FIG. 12 is a sectional view similar to a part of FIG. 4, showing an electric lock assembly, but with operating key removed.

FIG. 13 is a reduced perspective view of a switch lock member employed in the electric lock of FIG. 12.

FIG. 14 is a reduced perspective view of key employed in operating the lock of FIG. 12.

FIG. 15 and FIG. 17 are sectional view of fifth and sixth coupling devices.

FIG. 16 is a diagram of an electrical control circuit for the device of FIG. 15, using the lock assembly of FIG. 12.

FIG. 18 is a diagram of en electrical control circuit for the device of FIG. 17.

Referring first to FIG. I, there is shown a truck trailer coupling device 10 comprising an axially vertically movable hitch or kingpin l2 terminating in a head 14 having an annular recess 16. The pin is adapted for engaging in a hole 17 of a coupling plate 18 carried by a tractor (not shown). The pin 12 has a bottom shoulder and is axially movable in an axially vertical casing 20 between retracted and extended positions. The casing is an extension of a baseplate 22 secured by bolts 24 to the floor 26 of a truck trailer 25. The plate is formed with a peripheral bevel 28 to prevent engagement by a chain or other unauthorized coupling means. Pin 12 is shown retracted in casing 20 so that head 14 is flush with the bottom of plate 22 and is held stationary in hole 30 in the plate by engagement of its shoulder about the top thereof. A longitudinal groove 32 is formed in pin 12. A longitudinal key 34 extends laterally into groove 32 and prevents rotation of the pin while permitting longitudinal slidable movement of the pin.

In the pin is an axial, threaded bore 36. A threaded shaft 38 extends into bore 36. This shaft is secured to and rotates with a worm gear 40 located in a gearbox 42 secured on top of the casing. The box has a cover plate 44. Engaged with gear 40 is an axially horizontal worm 45 carried by a shaft 46. One end of the shaft is coupled via a slip clutch 48 to shaft 49 of a motor 50 mounted on one side of gearbox 42 to permit the motor to overrun the pin upon reaching full extended or retracted position. The other end of shaft 46 is secured by coupling 47 to shaft 52. Shaft 52 extends horizontally through a cylindrical housing 54 secured to the other side of the gearbox. A lockable crank drive assembly 60 is located in a cavity 55 at the outer end of the housing. A locking tongue or bar 62 can be extended radially from the barrel 64 of the assembly to engage in a recess 65 in the housing to prevent rotation of the barrel and shaft 52. At the outer end of the barrel is a diametral ridge 66 which can receive a diametral groove 68 formed in a cylindrical body 70 of a crank 72, shown to best advantage in FIGS. 2, 4, 6 to which reference is now made.

In body 70 of the crank is a recess 74 in which head 75 of a key 76 is longitudinally slidable. A pin 77 fixed in body 70 extends through a slot 78 in the head of the key. The key has a serrated shank 73 extending outwardly of the crank for engaging in a lock cylinder 80 rotatable in lock body 84 in barrel 64, and held against rotation by pins 82. The arrangement of pins in the lock is conventional. The cylinder 80 is rotatable by key 76 when shank 73 is fully inserted into the keyhole or slot 85 of cylinder plate 87. The key is urged outwardly of the crank body by a coil spring 86 set in a recess 88 and bearing on the head of the key. Crank 72 has a handle 88 to facilitate manual turning of the crank. The crank can be engaged with the barrel 64 of assembly 60 which is rotatably disposed in housing 54. The outer end of the housing is tightly set in opening 90 in the front wall 96 of trailer 25.

Referring further to FIGS. 3, 4 and 6, the outer end plate 87 of cylinder 80 is exposed at the outer end of barrel 64. A discontinuity is provided in ridge 66 where the end plate 87 of the cylinder is exposed. At the inner end of the cylinder is a disk 92 secured by screws 93. Extending outwardly of the disk is a bent stub shaft 95 having an offset end 94 engaged in a slot 97 located at the bottom end or head 98 of T-shaped tongue or bar 62. The shaft of the tongue is axially slidable in a radial passage 99 formed in barrel 64. The tongue 62 can be moved between an upper extended position shown in FIG. 4 and a lower retracted position shown in FIG. 6. Disk 92, plate 87,

and the head 98 of the tongue move in a chamber 100 formed inside the barrel 64. The outer end of the tongue engages in recess 65 of housing 54 in the locked position of the assembly. When the tongue is so extended the barrel 64 cannot be rotated. Shaft 52 terminates at a radial annular flange 102 secured to the inner end of barrel 64 by screws 104. Thus the shaft is prevented from rotation when the assembly is locked. In turn, the worm 45 and worm gear 40 shown in FIG. 1 are prevented from rotation. Thus the pin 12 is held stationary. The pin can be held in either retracted position shown by solid lines in FIG. 1 or in extended position as shown by dotted lines.

To move the pin 12 axially into the retracted or extended position, the key 76 is first inserted into lock cylinder 80. This position of the key is indicated in FIG. 4. At this point the ridge 66 of barrel 64 and groove 68 in crank body 70 are disengaged. The crank can be turned to rotate lock cylinder 80 and cause tongue 62 to retract out of recess 65 in housing 54. Then the crank body can be pushed axially to engage ridge 66 and groove 68. Now the barrel 64 can be rotated by means of the crank until the pin 12 is located in the desired extended or retracted position. It will be apparent that the key 76 and cylinder 80 revolve with the barrel 64 and do not turn with respect to the barrel since the position of the key remains fixed in the crank body. Pin 77 moves forward in slot 78 to the position shown in FIG. 6 when the crank is advanced to engage the ridge 66 of the barrel. After removal of the crank and key from assembly 60, the pin 12 remains fixed in position in casing 20.

If motor drive of the pin is desired, then the circuit 125 shown in FIG. 7 will be employed. Motor 50 is connected in series with a three-position reversing switch 126 and battery 128. If switch 126 is thrown from OFF position to either RETRACT PIN or EXTEND PIN position, the motor will be energized and will turn. However, the shaft 52 will not turn due to slippage at clutch 48, unless locking tongue 62 is retracted. If the assembly 60 is unlocked by use of key 76 then the motor can be turned on to drive the shaft 52 for retracting or extending pin 12.

FIGS. 8 and 9, show another coupling device 10A installed in truck trailer 2511. The device is similar to device 10 of FIG. 1-6 and corresponding parts are identically numbered. Device 10A is adapted for coupling to a tractor of the type having a pin 130 on its coupling plate 132. In device 10A, baseplate 22a is formed with a tapered, undercut slot 133 terminating at hole 30a in the plate. Pin 12a is like pin 12 except that head 14a is entirely cylindrical and occupies hole 30a in the locked position of the device. Then head 12a obstructs hole 30a and its bottom end is flush with the bottom of plate 220. This prevents engagement of pin 130 in hole 30a. Pin 12a is retracted and extended by means of lock assembly 60 in the same manner as described above, and motor drive can be used by means of circuit 125 in the same manner as described in connection with FIG. 7. In assembly 10A pin 12a is extended downwardly to block hole 30a in the locked position of the device, while in assembly 10, pin 12 is retracted in hole 30 in the locked position of the device.

FIG. 10 shows another coupling device 108 which also employs lock assembly 60. Coupling device 108 is similar to device 10A of FIGS. 8 and 9, in that it employs a slotted baseplate 22a for engaging the coupling pin of a tractor. Pin 12b is axially slidable in a sleeve guide 150 mounted on the floor 26 of trailer 25b. The pin is held retracted from hole 30a in plate 22a by a coil spring 151 on the pin located between conical top 152 and the top of the sleeve guide. The pin 12b can be moved axially downward to block hole 300 so that the coupling pin of an authorized tractor cannot be engaged therein.

In order to push pin 12b axially downward, a wedge 154 is secured to the-inner end of a threaded shaft 156 engaged in threaded bore 158 inside of rotatable shaft 52'. When locking tongue 62 is disengaged from recess 65 in housing 54', shaft 52' and barrel 64 can be turned by crank 72. Shaft 52' will rotate with barrel 64 to advance or retract threaded shaft 156. Shaft 156 has a radial pin 160 engaged in a slot 162 in housing 54 to prevent rotation of the shaft. Housing 54 is secured by flange 164 and bolts 166 to front wall 96 of the trailer. It will be evident that rotation of barrel 64 will axially advance or retract shaft 156. When shaft 156 advances wedge 154 it causes pin 12b to move down. When shaft 156 is retracted, spring 151 retracts pin 12b. The pin can be locked in the extended position blocking hole 30a, by use of key 76 to rotate cylinder 80 and extend tongue 62 in the same manner as described in connection with coupling device 10.

FIG. 11 shows coupling device which is like device 10b and corresponding parts are identically numbered. Device 100 is adapted for engaging the slotted coupling plate of a tractor in a manner similar to coupling device 10. A head 14 with circumferential recess 16 is formed at the bottom end of pin 120. When pin is extended axially downward out of hole 30 in baseplate 22 to the dotted line position and shouldered about the plate hole 30, it can be engaged by the coupling plate of the tractor. When the pin is retracted to the full line position shown in FIG. 11, with head 14 flush with the bottom of baseplate 22, an unauthorized tractor cannot be coupled to trailer 25c. Pin 120 is extended by axial movement of shaft 156 and engagement of wedge 154 with conical end 152 of the pin in the same manner as described in connection with coupling device 1013. When shaft 156 is retracted, spring 151 retracts pin 12c. Both devices 10b and 100 are provided with a metal shield secured inside the trailer to prevent tampering with parts of the coupling device. A similar shield can be provided for the parts of coupling devices 10 and 10A in trailers 25 and 250.

FIG. 12 shows another lock assembly 60a which is arranged like assembly 60 of FIGS. 4 and 6 and corresponding parts are identically numbered. In assembly 6011, cylinder 80a extends outwardly of the inner end of lock body 84 and carries disk 92. Disk 92 supports and rotates bent shaft 95 which engages axially movable T-bar 62. The lock body 84 is secured in barrel 64a. This barrel is rotatable in housing 54a. This housing is secured by bolts 200 extending through holes in flange 202 engaged in threaded holes 204 in the wall 96a of trailer 25d. An externally threaded collar 210 is screwed into an inner threaded portion of housing 54a. A cylindrical switch block 212 has a cylindrical head 214 engaged in the collar 210. The head 214 has a recess 216 at its inner end. Four notches 218 are formed in flange 220 around recess 216. Four pushbutton switches 222 are engaged in holes 224 in head 214; see FIG. 13. Tongues 226 of the switches extend into the notches. lnsulated conductors 228 extend from the switches and terminates at conductive concentric rings 230, 232 of terminal ring 234. Wires 236 and 238 are connected to the rings 230, 232. These wires are connected in a circuit 250 shown in FIG. 16 and described below. A friction ring 240 engaged in the collar bears on block 212 to inhibit rotation. A friction pad 242 is urged by a coil spring 244 against the side of barrel 64a to inhibit rotation. The coil spring and pad are disposed in a lateral bore 247 formed in the side of housing 54a.

The locking assembly 60a is arranged to operate the drive motor 50a of coupling device 10d shown in FIG. 15. Referring to FIG. 15, it will be noted that motor 50a is carried by brackets 251 on a supporting plate 252. Plate 252 is mounted on floor 254 of trailer 25d. The motor drives a worm 256 journaled in bearing 258 carried by bracket 260 on casing wall 170a. The worm drives a worm gear sector 262 bolted to pin body 264. The pin body is a disklike member which is rotatably mounted on a transverse shaft 266 supported between sidewalls 268 of casing 170a. The pin body is integral with pin 12d which can be rotated between an axially vertical position and an axially horizontal position. The horizontal position is shown in dotted lines in FIG. 15. The motor 50a is reversible and will drive the pin up or down. When the pin is rotated it moves through registering slots 272 and 274 in floor 254 and in plate 275.

The motor is driven when circuit 250 shown in FIG. 16 is actuated. In this circuit motor 50a has terminals 280, 282 connected to crossed contacts of switch 290. This switch can be located at any convenient place for manual operation. Switch 290 is a reversing switch and has two poles 291, 293 movable to OFF, UP and DOWN positions. Switches 222 actuated by buttons or tongues 226 are connected in parallel to conductive rings 230, 232. Ring 230 is connected via wire 236 to one terminal of battery 292. Ring 232 is connected by wire 238 to pole 291. Pole 293 is connected to the other battery terminal, by the arrangement shown. When any tongue 226 is pressed to close a switch 222, the reversing switch can be set from OFF position to UP or DOWN position. The motor will then drive worm 256 shown in FIG. in one direction or the other for raising or lowering pin 12d.

It will be noted that the locking assembly 60a shown in FIG. 12 is in effect locked when bar 62 is retracted. If the bar is retracted from flange 220 of head 214 then all switches 222 are open. Motor 50a cannot then be turned on and pin 12d remains in up or down position wherever it was set last. If an unauthorized person attempts to turn barrel 64a by means of some tool, this will have no effect on lock 84. The lock can be opened, i.e., bar 62 can only be moved axially outward to close a switch 222 by use of a proper key. A crank-key such as shown in FIG. 2 can be used for this purpose. However, the crank part is not necessary and can be omitted. This construction is shown in FIG. 14 where key 76 is slidable in recess 74 and is spring biased outwardly in the same manner as indicated in FIGS. 4 and 6. Cylindrical body 70a is knurled to facilitate manual turning.

In the assembly of FIG. 15 there is no direct mechanical drive between the lock assembly and the pin. Instead the motor is actuated by the electric lock when a proper key is inserted to advance bar 62 axially into any one of notches 218 to push back a tongue 226 and close the associated switch 222. Closure of any one switch will enable operation of the motor by means of switch 290.

Instead of an electric motor a hydraulic motor can be used. This is shown in FIG. 17 when coupling device We is installed in trailer 25d. I-Iere cylinder 300 has an axially movable piston 302 connected to piston shaft 304. The shaft is connected eccentrically by pin 306 to disklike pin body 264a. The pin body is rotatably carried by shaft 266a between walls 268 of casing 170a. Pin body 2640 carries pin 12e which can be rotated through slots 272, 274 of the trailer floor and baseplate 275. Conduit 310 is connected to the cylinder at one end and conduit 312 is connected to the cylinder near the other end. The cylinder is pivotally mounted on shaft 314 carried by bracket 316. When the piston shaft is extended as shown in FIG. 17, pin 12e extends axially downward. When the piston shaft is retracted, the pin body and pin are rotated and the pin extends axially horizontally. The pin remains in the axially downward position due to the overcenter thrust of the piston shaft when fully extended. The piston shaft is held extended by air pressure through the system 350 shown in FIG. 18.

A compressed air supply from a tank or compressor 351 is applied to the cylinder 300 via main conduit 352 and branch conduit pipes 310, 312. Electrically operated valves 354 and 356 in the pipes 310, 312 are connected to reversing switch 290a arranged in a manner similar to that shown in circuit 250 of FIG. 16. Valve 354 is connected to switch contacts 360. Valve 346 is connected to switch contacts 362. When the switch poles are thrown to UP position valve 356 is operated to admit air to the cylinder 300 and shaft 304 is retracted to turn pin 122 up. When the switch poles are thrown to DOWN position then valve 354 is operated to admit air to the cylinder and piston shaft 304 is extended to lower the pin 12e. Switches 222 of which only one is shown are operated by extension of bar 62 into one of notches 218 as explained in connection with FIG. 12. The locking assembly 60a of FIG. 12 will serve equally well for the electric or hydraulic motor drive of the pin 12d or 12.

In the drawings, the springs, cams, gearing and other mechanical devices conventionally used to hold the coupling pin of the tractor or trailer in engagement with the slotted coupling plate of the trailer or tractor respectively have been omitted in order to show the parts of the present invention more clearly.

Devices embodying the invention can be installed in trailers as original equipment or can be made up in kit form for installation in existing trailers. They will fulfill a long felt need for foolproof means to defeat theft or high jacking of truck trailers.

While the invention has been described particularly as applied particularly to the coupling of tractors and trailers it will be apparent that the principles of the invention can be employed in other coupling applications where heavy duty, secure, foolproof coupling is required. Among such coupling applications are:

a. marine uses, as coupling tugs to barges and other towed loads;

b. aircraft uses, as coupling helicopters and other aircraft to other airbourne loads;

0. space travel uses, as coupling space vehicles and parts of space vehicles;

(1. underwater uses, as coupling submarines to underwater barges and other loads.

e. amphibious uses as coupling of transports, etc.

What is claimed is:

1. A device for preventing unauthorized coupling of a tractor to a trailer, comprising a baseplate mountable upon the trailer, said baseplate having a hole therein, an axially movable hitch pin adapted for coupling a trailer to a trailer tractor. drive means for moving said hitch pin between retracted and extended positions, said hitch pin 'being shouldered for cngagement with the baseplate about the top of the hole and adapted to be extended so that its head extends below the baseplate in the extended position, said hitch pin upon being retracted inside the trailer will have its head withdrawn into the hole in the baseplate and inaccessible, motor means connected to the drive means for moving the pin to either of retracted or extended positions, a lock operated by a key and means interconnecting said drive means and lock so that the hitch pin can be selectively extended or retracted either by the keylock or by the motor upon opening the lock whereby the hitch pin can be so positioned in the said plate hole as to prevent coupling of the trailer to the tractor.

2. A device for preventing unauthorized coupling of a tractor to a trailer, comprising a baseplate mountable underneath the trailer, said plate having a hole therein; a pin adapted for coupling a trailer and tractor; means movably supporting said pin in either of two positions, said pin extending through said hole in the baseplate and below the baseplate in one of said positions, said pin being retracted inside the trailer in the other one of said positions; motor means for moving the pin to either of said positions respectively, a lock operated by a key; and means interconnecting the said motor means and lock so that the pin can be selectively extended and retracted; an axially vertical, cylindrical hollow guide member extending upwardly from said plate, said hole in the baseplate communicating with said guide member, said pin being disposed axially vertical in said guide member for axial movement in said hole in the plate; a stationary, axially horizontal cylindrical housing; a shaft rotatable in said housing; a rotatable barrel joined to said shaft for turning with the shaft; said lock being disposed in said barrel and operable by said key for preventing rotation of the barrel and shaft; said motor means comprising mechanical means arranged to operatively interconnect said pin and shaft so that said pin moves axially when said shaft is rotated, whereby the pin can be so positioned in said hole as to prevent coupling of the tractor to the trailer, said barrel having an exposed end arranged for engagement by a crank for manually turning the barrel.

3. A device as defined in claim 2, wherein further comprising spring means engaging said pin and normally retracting the same, so that the pin is extended in said hole only by rotational operation of said shaft; said mechanical coupling means comprising another shaft movable axially by the first-named shaft while rotating, said other shaft having a wedge-shaped tip and a conical top on said pin engageable by said wedge-shaped tip for advancing said pin in said hole in the plate.

4. A device as defined in claim 2, wherein said lock comprises rotatable cylinder, and a bar coupled to said cylinder and movable radially in said barrel to engage said housing for preventing rotation of the barrel.

5. A device as defined in claim 4, wherein said barrel has an exposed end with a diametral ridge thereon, and further comprising a crank having a cylindrical body formed with a groove for engaging said ridge to turn the barrel, and a key slidably mounted in said body of the crank and spring biased to extend axially outward of said body, said cylinder havinga keyhole at the exposed end of the barrelfor receiving said key, whereby the crank can be turned to unlock the lock when the key is engaged therein while the ridge and groove are out of engagement with each other, and whereby the crank can be advanced to engage said ridge and groove for turning the barrel while the key remains in said lock and turns with the barrel and crank.

6. A device as defined in claim 5, wherein said mechanical means comprises a worm carried by said shaft, and a worm wheel connected to said pin and engaged with said worm, whereby rotation of the worm causes axial movement of said pm,

7. A device as defined in claim 6, further comprising a motor connected to said shaft for turning the same to cause axial movement of said pin,

8. A device as defined in claim 6, further comprising spring means engaging said pin and normally retracting the same, so that the pin is extended in said hole in the plate only by rotational operation of said shaft.

9. A device for preventing the unauthorized coupling of a tractor to a trailer comprising a baseplate mountable underneath the trailer, said plate having a hole therein; a pin adapted for coupling a trailer and tractor; means movably supporting said pin in either of two positions, said pin extending through said hole in the baseplate and below the baseplate in one of said positions, said pin being retracted inside the trailer in the other one of said positions; motor means for moving the pin to either of said positions respectively, a lock operated by a key; and means interconnecting the said motor means and lock so that the pin can be selectively extended and retracted; said means movably supporting the pin comprises a pin body; a shaft rotatably supporting said pin body above said plate so that the pin is rotatable between said two positions; said lock including switch means; said means interconnecting the motor means and lock, comprising an electric circuit and power supply, whereby the pin can be selectively moved to either position when said circuit is closed by operation of the lock by said key.

10. A device as defined in claim 9, wherein said motor means is connected to the pin body by a piston shaft which assumes an overcenter position with respect to the pin body when the pin is rotated to vertical position extending below said plate. 

1. A device for preventing unauthorized coupling of a tractor to a trailer, comprising a baseplate mountable upon the trailer, said baseplate having a hole therein, an axially movable hitch pin adapted for coupling a trailer to a trailer tractor, drive means for moving said hitch pin between retracted and extended positions, said hitch pin being shouldered for engagement with the baseplate about the top of the hole and adapted to be extended so that its head extends below the baseplate in the extended position, said hitch pin upon being retracted inside the trailer will have its head withdrawn into the hole in the baseplate and inaccessible, motor means connected to the drive means for moving the pin to either of retracted or extended positions, a lock operated by a key and means interconnecting said drive means and lock so that the hitch pin can be selectively extended or retracted either by the keylock or by the motor upon opening the lock whereby the hitch pin can be so positioned in the said plate hole as to prevent coupling of the trailer to the tractor.
 2. A device for preventing unauthorized coupling of a tractor to a trailer, comprising a baseplate mountable underneath the trailer, said plate having a hole therein; a pin adapted for coupling a trailer and tractor; means movably supporting said pin in either of two positions, said pin extending through said hole in the baseplate and below the baseplate in one of said positions, said pin being retracted inside the trailer in the other one of said positions; motor means for moving the pin to either of said positions respectively, a lock operated by a key; and means interconnecting the said motor means and lock so that the pin can be selectively extended and retracted; an axially vertical, cylindrical hollow guide member extending upwardly from said plate, said hole in the baseplate communicating with said guide member, said pin being disposed axially vertical in said guide member for axial movement in said hole in the plate; a stationary, axially horizontal cylindrical housing; a shaft rotatable in said housing; a rotatable barrel joined to said shaft for turning with the shaft; said lock being disposed in said barrel and operable by said key for preventing rotation of the barrel and shaft; said motor means comprising mechanical means arranged to operatively interconnect said pin and shaft so that said pin moves axially when said shaft is rotated, whereby the pin can be so positioned in said hole as to prevent coupling of the tractor to the trailer, said barrel having an exposed end arranged for engagement by a crank for manually turning the barrel.
 3. A device as defined in claim 2, wherein further comprising spring means engaging said pin and normally retracting the same, so that the pin is extended in said hole only by rotational operation of said shaft; said mechanical coupling means comprising another shaft movable axially by the first-named shaft while rotating, said other shaft having a wedge-shaped tip and a conical top on said pin engageable by said wedge-shaped tip for advancing said pin in said hole in the plate.
 4. A device as defined in claim 2, wherein said lock comprises rotatable cylinder, and a bar coupled to said cylinder and movable radially in said barrel to engage said housing for preventing rotation of the barrel.
 5. A device as defined in claim 4, wherein said barrel has an exposed end with a diametral ridge thereon, and further comprising a crank having a cylindrical body formeD with a groove for engaging said ridge to turn the barrel, and a key slidably mounted in said body of the crank and spring biased to extend axially outward of said body, said cylinder having a keyhole at the exposed end of the barrel for receiving said key, whereby the crank can be turned to unlock the lock when the key is engaged therein while the ridge and groove are out of engagement with each other, and whereby the crank can be advanced to engage said ridge and groove for turning the barrel while the key remains in said lock and turns with the barrel and crank.
 6. A device as defined in claim 5, wherein said mechanical means comprises a worm carried by said shaft, and a worm wheel connected to said pin and engaged with said worm, whereby rotation of the worm causes axial movement of said pin.
 7. A device as defined in claim 6, further comprising a motor connected to said shaft for turning the same to cause axial movement of said pin.
 8. A device as defined in claim 6, further comprising spring means engaging said pin and normally retracting the same, so that the pin is extended in said hole in the plate only by rotational operation of said shaft.
 9. A device for preventing the unauthorized coupling of a tractor to a trailer comprising a baseplate mountable underneath the trailer, said plate having a hole therein; a pin adapted for coupling a trailer and tractor; means movably supporting said pin in either of two positions, said pin extending through said hole in the baseplate and below the baseplate in one of said positions, said pin being retracted inside the trailer in the other one of said positions; motor means for moving the pin to either of said positions respectively, a lock operated by a key; and means interconnecting the said motor means and lock so that the pin can be selectively extended and retracted; said means movably supporting the pin comprises a pin body; a shaft rotatably supporting said pin body above said plate so that the pin is rotatable between said two positions; said lock including switch means; said means interconnecting the motor means and lock, comprising an electric circuit and power supply, whereby the pin can be selectively moved to either position when said circuit is closed by operation of the lock by said key.
 10. A device as defined in claim 9, wherein said motor means is connected to the pin body by a piston shaft which assumes an overcenter position with respect to the pin body when the pin is rotated to vertical position extending below said plate. 